Low attenuation optical fiber

ABSTRACT

An optical waveguide fiber comprises: (a) a core with a refractive index profile having, a radius, an alpha and a relative refractive index characterized by delta % that varies along the radius; (b) at least one cladding surrounding the core; wherein the alpha is less than 2.5, peak refractive index delta % is between 0.34% and 0.4%, the relative refractive index is less than 0.01% for all radii greater than 7 μm, and this optical waveguide fiber has a mode field diameter MFD at a wavelength of 1310 nm of no more than 9.54 μm, and attenuation less than: (a) 0.329 dB/km at a wavelength of 1310 nm, (b) 0.290 dB/km at a wavelength of 1383 nm, (c) 0.255 dB/km at a wavelength of 1410 nm, and (d) 0.189 dB/km at a wavelength of 1550 nm.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to optical fibers, andparticularly to optical fibers with low attenuation and low Small AngleScattering (SAS) loss.

2. Technical Background

Telecommunication systems, for the underground and undersea applicationsin particular, require optical fiber which is capable of transmittingsignals for a long distance without degradation. The appearance of newtechnologies, such as wavelength division multiplexing (WDM) and highchannel speed, makes possible to satisfy the ever-growing demand fornetwork bandwidth. However, the optical fiber attributes such asattenuation and bend loss contribute to the degradation of the signal.

US patent publication 2003/0161597 discloses an optical fiber capable ofmulti mode operation at wavelengths below 1300 nm and single modeoperation at wavelengths above 1300 nm. The publication describes thatthis optical fiber has reduced intermodal noise, but is silent withregard to overall attenuation and Small Angle Scattering (SAS) loss.

The article by Rawson E. G., entitled “Measurement of the AngularDistribution of Light Scattered from a Glass Fiber Optical Waveguide”,App. Opt. 11, 2477 (1972) describes the measurement of angulardistribution of a near-forward scattering, and proposes that it iscaused by narrow dielectric needles aligned with the fiber axis.

The article by Rawson E. G., entitled “Analysis of Scattering from FiberWaveguide with Irregular Core Surfaces”, App. Opt. 13, 2370 (1974)describes an induced-dipole scattering method and presents the resultsof the angular distribution of scattering for five types ofperturbations on the core-cladding interface of the optical fiber.

The article by Lines, M. E., Reed W. A., Di Giovanni D. J. and HamblinJ. R., entitled “Explanation of Anomalous Loss in High Delta Single modeFibers”, Ele. Lett., 35, 1009 (1999) describes the angular dependence ofanomalous scattering is caused by fluctuation of refractive index of thematerial along axial and azimuthal directions. The loss is predicted tobe related the fiber profile peak and profile shape.

SUMMARY OF THE INVENTION

According to one aspect of the invention, an optical waveguide fibercomprises:

-   -   a core with a refractive index profile having, a radius, an        alpha and a relative refractive index characterized by delta %        that varies along the radius; and    -   at least one cladding surrounding the core;    -   wherein the alpha is less than 2.5, peak refractive index delta        % in said core is between 0.34% and 0.4%, the relative        refractive index is less than 0.01% for all radii greater than 7        μm, and this optical waveguide fiber has a mode field diameter        MFD at a wavelength of 1310 nm of no more than 9.54 μm, and        attenuation less than: (a) 0.329 dB/km at a wavelength of 1310        nm, (b) 0.290 dB/km at a wavelength of 1383 nm, (c) 0.255 dB/km        at a wavelength of 1410 nm, and (d) 0.189 dB/km at a wavelength        of 1550 nm.

According to some of the embodiments, the optical waveguide fiber hasattenuation that is less than: (a) 0.322 dB/km at a wavelength of 1310nm, (b) 0.270 dB/km at a wavelength of 1383 nm; (c) 0.247 dB/km at awavelength of 1410 nm, and (d) 0.179 dB/km attenuation at a wavelengthof 1550 nm.

According to some embodiments, the optical waveguide fiber comprises:

-   -   (a) a core with a refractive index profile having, a radius, an        alpha and a relative refractive index that varies along said        radius; and at least one cladding surrounding the core; wherein        the relative refractive index (delta %) is less than 0.01% for        all radii greater than 6 μm, and this optical waveguide fiber        has a mode field diameter MFD at a wavelength of 1310 nm of less        than 9.4 μm.

One advantage of this fiber is that it has low attenuation and low smallangle scattering (SAS). Because of the low attenuation and/or low SASlosses, this optical waveguide fiber can either eliminate or reduce thenumber of signal amplifiers needed for a network, which can reduce thecost of the network.

Additional features and advantages of the invention will be set forth inthe detailed description which follows, and in part will be readilyapparent to those skilled in the art from that description or recognizedby practicing the invention as described herein, including the detaileddescription which follows, the claims, as well as the appended drawings.

It is to be understood that both the foregoing general description andthe following detailed description present embodiments of the invention,and are intended to provide an overview or framework for understandingthe nature and character of the invention as it is claimed. Theaccompanying drawings are included to provide a further understanding ofthe invention, and are incorporated into and constitute a part of thisspecification. The drawings illustrate various embodiments of theinvention, and together with the description serve to explain theprinciples and operations of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates schematically one embodiment of the optical waveguidefiber.

FIGS. 2 a–2 c are refractive index profiles of exemplary optical fibersaccording to some of the embodiments of the present invention;

FIG. 3 illustrates schematically Small Angle Scattering (SAS) of anoptical waveguide fiber.

FIG. 4 is a graph of two different types of scattering intensity as afunction of scattering angle in optical waveguide fiber.

FIG. 5 is a graph of scattering intensity as a function of scatteringangle in two different fiber types.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the present preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Whenever possible, the same reference numeralswill be used throughout the drawings to refer to the same or like parts.One embodiment of the optical fiber waveguide of the present inventionis shown in FIG. 1, and is designated generally throughout by thereference numeral 10.

In accordance with the invention the optical waveguide fiber includes acore 12 and at least one cladding 14 surrounding the core 12. In theseexemplary embodiments the cladding 14 is pure silica and the silica core12 is doped with Ge to obtain the desired change in relative refractiveindex (3.5–4.2 mole % of Ge). The diameter of the core 12 varies from 9μm to 16 μm. The outer diameter of the cladding 14 of these exemplaryoptical fibers 10 is about 125 μm. The exemplary refractive index fiberprofiles of these optical waveguide fibers 10 are depicted in FIGS. 2a–2 c (profiles a–k). More specifically, in these figures, the verticalaxes correspond to the delta % (relative to that of pure silicacladding) and the horizontal axes correspond to fiber radius. The coreDelta % of these optical fibers 10 corresponding to FIGS. 2 a–2 c isdefined as

${\Delta = {\frac{\left( {{n(r)}^{2} - n_{0}^{2}} \right)}{2{n(r)}^{2}} \times 100}},$where n₀ is the refractive index of the cladding 14 and n is therefractive index of the core 12, at a radial distance r away from thecenterline. It is noted that neither fluorine doping nor germaniumup-doping in the cladding are required to achieve these fiber profiles.

The Delta % values corresponding to profiles (a)–(k) shown in FIGS. 2a–2 c are given in Tables 1a and 1b, below.

TABLE 1a a b.1 b.2 c d e Delta (r = 0) % 0.348 0.389 0.389 0.372 0.3990.360 Delta (r = 0.5) % 0.348 0.387 0.388 0.372 0.396 0.360 Delta (r= 1) % 0.348 0.381 0.381 0.372 0.387 0.360 Delta Max % 0.348 0.389 0.3890.372 0.399 0.360 r (Delta Max) um 0.000 0.000 0.000 0.000 0.000 0.000Delta (r = 1.5 um) % 0.348 0.370 0.369 0.372 0.372 0.358 Delta (r = 2um) % 0.348 0.353 0.352 0.372 0.351 0.340 Delta (r = 2.5 um) % 0.3470.330 0.327 0.372 0.325 0.311 Delta (r = 3 um) % 0.334 0.301 0.297 0.3490.292 0.275 Delta (r = 3.5 um) % 0.296 0.264 0.259 0.264 0.254 0.232Delta (r = 4 um) % 0.232 0.221 0.214 0.233 0.210 0.184 Delta (r = 4.5um) % 0.140 0.170 0.162 0.186 0.160 0.132 Delta (r = 5 um) % 0.022 0.1110.103 0.124 0.104 0.074 Delta (r = 5.5 um) % 0.000 0.046 0.036 0.0470.042 0.014 Delta (r = 6 um) % 0.000 0.004 0.000 0.001 0.000 0.000 Delta(r = 6.5 um) % 0.000 0.000 0.000 0.000 0.000 0.000 Delta (r = 7 um) %0.000 0.000 0.000 0.000 0.000 0.000 Delta (r = 7.5 um) % 0.000 0.0000.000 0.000 0.000 0.000 Delta (r = 8 um) % 0.000 0.000 0.000 0.000 0.0000.000

TABLE 1b f g h i j k Delta (r = 0) % 0.360 0.360 0.372 0.372 0.355 0.350Delta (r = 0.5) % 0.360 0.360 0.372 0.372 0.355 0.350 Delta (r = 1) %0.360 0.360 0.371 0.372 0.355 0.350 Delta Max % 0.360 0.360 0.372 0.3720.355 0.350 r (Delta Max) um 0.000 0.000 0.000 0.000 0.000 0.000 Delta(r = 1.5 um) % 0.358 0.360 0.369 0.371 0.355 0.350 Delta (r = 2 um) %0.342 0.357 0.361 0.368 0.354 0.349 Delta (r = 2.5 um) % 0.315 0.3360.341 0.355 0.347 0.343 Delta (r = 3 um) % 0.281 0.303 0.306 0.324 0.3230.323 Delta (r = 3.5 um) % 0.241 0.263 0.262 0.273 0.270 0.278 Delta (r= 4 um) % 0.196 0.215 0.214 0.213 0.197 0.209 Delta (r = 4.5 um) % 0.1470.162 0.160 0.150 0.131 0.134 Delta (r = 5 um) % 0.093 0.103 0.102 0.0870.084 0.070 Delta (r = 5.5 um) % 0.036 0.040 0.051 0.036 0.047 0.027Delta (r = 6 um) % 0.000 0.000 0.019 0.010 0.020 0.007 Delta (r = 6.5um) % 0.000 0.000 0.005 0.002 0.006 0.001 Delta (r = 7 um) % 0.000 0.0000.001 0.000 0.001 0.000 Delta (r = 7.5 um) % 0.000 0.000 0.000 0.0000.000 0.000 Delta (r = 8 um) % 0.000 0.000 0.000 0.000 0.000 0.000

The optical fibers 10 are relatively easy to manufacture because of thesimplicity of the refractive index profiles. These optical waveguidefibers 10 have low attenuation compared to Corning's SMF-28® and thebending loss similar to that of Corning's SMF-28®.

According to some of the embodiments of the present invention an opticalwaveguide fiber 10 comprises: a core 12 with a refractive index profilehaving, a radius, an alpha and a relative refractive index characterizedby delta % that varies along said radius; at least one cladding 14surrounding the core 12; wherein the alpha is less than 2.5 and the peakrefractive index delta % is between 0.34% and 0.4%. It is preferablethat the refractive index delta % is less than 0.01% for all radiigreater than 7 μm. In these embodiments of the optical waveguide fiber10 the mode field diameter MFD at a wavelength of 1310 nm is no morethan 9.54 μm (and preferably less than 9.5 μm), and attenuation lessthan: (a) 0.329 dB/km at a wavelength of 1310 nm, (b) 0.290 dB/km at awavelength of 1383 nm, (c) 0.255 dB/km at a wavelength of 1410 nm, and(d) 0.189 dB/km at a wavelength of 1550 nm. In some embodiments MFDdiameter at 1310 nm was in the 8.9 μm to 9.4 μm range. It is preferablethat the optical waveguide fiber 10 has attenuation that is less than:(a) 0.322 dB/km at a wavelength of 1310 nm, (b) 0.275 dB/km (andpreferably less than 0.270) at a wavelength of 1383 nm; (c) 0.247 dB/kmat a wavelength of 1410 nm, and (d) 0.179 dB/km attenuation at awavelength of 1550 nm.

The optical waveguide fibers 10 have low attenuation and small SmallAngle Scattering (SAS), at least in part due to their low-alpha profiles(i.e., alpha less than 2.5). The low-alpha profiles produce a gradualchange of refractive index, which contributes to decreased loss due toSmall Angle Scattering (SAS).

The Small Angle Scattering (SAS) of the exemplary fibers 10 (profilesa–k) is less than 0.006 dB/kin at the wavelength of 1550 nm. It is morepreferable that SAS is less than 0.002 dB/km at the wavelength of 1550nm. It is preferable that the SAS be less than 0.0081 dB/km and morepreferably less than 0.0025 dB/km at the wavelength of 1300 nm. It ispreferable that the SAS be less than 0.007 dB/km and more preferablyless than 0.002 dB/km at the wavelength of 1400 nm.

The bend resistance of an optical waveguide fiber can be gauged byinduced attenuation under prescribed test conditions.

One type of bend test is the lateral load microbend test. In thisso-called “lateral load” test, a prescribed length of waveguide fiber isplaced between two flat plates. A #70 wire mesh is attached to one ofthe plates. A known length of the optical waveguide fiber is sandwichedbetween the plates and a reference attenuation is measured while theplates are pressed together with a force of 30 newtons. A 70 newtonforce is then applied to the plates and the increase in attenuation indB/m is measured. The increase in attenuation is the lateral loadattenuation of the waveguide.

The “pin array” bend test is used to compare relative resistance of anoptical waveguide fiber to bending. To perform this test, attenuationloss is measured for a waveguide fiber with essentially no inducedbending loss. The optical waveguide fiber is then woven about the pinarray and attenuation again measured. The loss induced by bending is thedifference between the two measured attenuations. The pin array is a setof ten cylindrical pins arranged in a single row and held in a fixedvertical position on a flat surface. The pin spacing is 5 mm, center tocenter. The pin diameter is 0.67 mm. During testing, sufficient tensionis applied to make the optical waveguide fiber conform to a portion ofthe pin surface.

It is preferable that the optical waveguide fiber 10 has Pin Arraymacrobend loss of less than 20 dB, and more preferable less than 10 dB,at the wavelength of 1550 nm. It is also preferable that the opticalwaveguide fiber 10 has a Lateral Load macrobend loss of less than 1.2dB/m, more preferably less than 0.7 dB/m at the wavelength of 1550 nm.

In the optical fiber 10 of the above described embodiments theStimulated Brillouin Scattering Threshold (SBSt) is higher than 8.2 dBm.It is preferable that SBSt be higher than 8.5 dBm. In some of theembodiments SBSt was 9.68 dBm. The SBSt values are specified for fiberlength of 20 km. It is also preferable that the optical waveguide fiberhas PMD of less than 0.1 ps/sqrt(km).

The calculated optical performances parameters for exemplary opticalfibers with profiles (a) through (k) (corresponding to FIGS. 2 a–2 c)are summarized in Table 2.

TABLE 2 MFD Dispersion slope Effective Area Cable Attenuation λo ® 1330nm D ® 1550 nm ® 1550 nm ® 1550 nm Cutoff at 1550 nm Profile (nm) (μm)(ps/(nm.km)) (ps/(nm².km)) (μm²) (nm) (dB/km) a 1310 9.20 16.85 0.058 831180 0.1874 b₁ 1314 9.29 16.96 0.060 84 1220 0.1852 b₂ 1316 9.25 16.730.059 83 1198 0.1853 c 1308 9.23 17.39 0.059 83 1261 0.1863 d 1318 9.2316.61 0.060 83 1194 0.1852 e 1323 9.29 16.01 0.059 85 1117 0.1855 f 13199.37 16.48 0.060 87 1156 0.1852 g 1313 9.34 16.97 0.059 85 1206 0.1856 h1314 9.29 16.92 0.060 84 1222 0.1855 i 1314 9.16 16.84 0.059 82 12170.1863 j 1314 9.29 16.77 0.059 85 1200 0.1862 k 1313 9.29 16.81 0.059 851187 0.1864

The additional optical parameters corresponding to the optical waveguidefibers with fiber profiles (a)–(k) are listed in Tables 3a and 3b, alongwith the Corning® SMF-28® attributes, for comparison. The opticalwaveguide fiber 10 of the embodiments depicted in FIGS. 2 a–2 c haveabout 0.00258–0.00481 dB/km lower attenuation at a wavelength of 1550nm, compared to SMF-28®.

TABLE 3a Lambda 0 slope 0 MFD 1310 F. Cutoff C. Cutoff Aeff 1310 unitsnm ps/nm{circumflex over ( )}2-km um nm nm um{circumflex over ( )}2SMF-28 1302- <0.0924 8.85–9.55 <1360 <1260 1322 A 1309.8  0.08686 9.204 1280  1180 65.965 b.1 1313.9  0.08912 9.294  1320  1220 65.907 b.21316.0  0.08892 9.251  1298  1198 65.178 C 1308.2  0.08876 9.233  1360 1261 65.871 D 1318.0  0.08917 9.227  1294  1194 64.659 E 1322.9 0.08817 9.286  1217  1117 65.308 F 1318.6  0.08865 9.374  1256  115666.717 G 1312.6  0.08854 9.343  1306  1206 66.876 H 1314.3  0.088969.294  1322  1222 65.978 I 1313.5  0.08828 9.162  1317  1217 64.501 J1314.4  0.08821 9.296  1300  1200 66.344 K 1312.5  0.08769 9.289  1287 1187 66.539

TABLE 3b D 1550 slope 1550 MFD 1550 Attn 1550 Microbend 1550 Macrobend1550 Aeff 1550 units ps/nm-km ps/nm{circumflex over ( )}2-km um dB/kmdB/m dB um{circumflex over ( )}2 a 16.8509 0.0583 10.463 0.18742 0.59510.002 83.125 b.1 16.9634 0.0601 10.591 0.18524 0.569 8.096 84.215 b.216.7342 0.0599 10.566 0.18533 0.616 9.439 83.680 c 17.3956 0.0597 10.4460.18631 0.349 4.404 82.656 d 16.6125 0.0601 10.556 0.18519 0.621 9.62283.365 e 16.0124 0.0597 10.711 0.18548 1.104 20.928 85.494 f 16.48030.0599 10.763 0.18521 0.989 16.508 86.530 g 16.9750 0.0597 10.6450.18565 0.660 9.768 85.231 h 16.9180 0.0601 10.596 0.18553 0.575 8.10484.309 i 16.8420 0.0595 10.430 0.18630 0.461 6.837 81.962 j 16.77530.0597 10.613 0.18618 0.668 10.080 84.728 k 16.8146 0.0592 10.5900.18645 0.682 10.858 84.602

The optical waveguide fiber with profile b was measured and the opticalparameters are provided in the following two tables:

TABLES 4 and 5 Attenuation Attenuation Attenuation AttenuationAttenuation MFD at 1310 nm at 1383 nm at 1410 nm at 1550 nm at 1625 nmat 1310 Lambda 0 Cable Cutoff (dB/km) (dB/km) (dB/km) (dB/km) (dB/km)(μm) (nm) (nm) Example 1 0.321 0.274 0.246 0.178 0.191 8.961 1318.01205.1 Example 2 0.326 0.262 0.247 0.186 0.200 9.195 1315.7 1209.4Example 3 0.323 0.278 0.249 0.181 0.193 9.079 1316.0 1207.8 Total dataset of 86 reels of fiber Min 0.321 0.259 0.246 0.178 0.191 8.891 1315.01178.1 Max 0.332 0.293 0.258 0.193 0.206 9.406 1321.4 1260.5 Average0.328 0.279 0.253 0.187 0.200 9.145 1317.0 1216.6

Corning® SMF-28® single-mode optical waveguide fiber is one of mostwidely deployed fibers. This fiber has a relatively small attenuation,which is mainly comes due to Rayleigh scattering. It is widely knownthat Rayleigh scattering has (1+cos²θ) distribution, where, θ is thescattering angle, as shown in FIG. 3. There is also excess scatteringbetween 0 and 60°, which is called Small Angle Scattering (SAS), whichis also shown in FIG. 3. Small Angle Scattering could be caused by thenon-uniform fiber profile variation along the transmission length. Thepresence of the small angle scattering is not desirable. It increasesthe total attenuation of the fiber. The optical waveguide fiberscorresponding to profiles (a)–(k) depicted in FIGS. 2 a–2 c are singlemode fibers that have very similar optical properties to those ofCorning® SMF-28®, but significantly lower Small Angle Scattering.

The SAS value of these optical waveguide fibers 10 is calculated asfollows:

The fiber profile can be expressed as:

-   -   n(r, a)=n₀+f(r, a), where, n₀ is the index of cladding, a is the        radius of core, n is the index of the core, and f can be any        function, then we define the parameter ε=n² which relates to the        perturbation at core-cladding interface. Any perturbation at        core-cladding interface, defined as dε/da, will cause small        angle scattering.

The scattering field E can be calculated from the changes along theaxial and azimuthal directions as G(z), and T(φ), respectively, by thefollowing equation:E=F(λ)∫∫∫E ⁰(r)G(z)T(φ)H(r,z,φ)dεrdrdφdz

-   -   where, F(ε) is a function of wavelength, E⁰(r) is the incident        field; H(r,z,φ) is the phase difference of scattering from        different locations of the optical waveguide fiber 10.

The scattering power is defined as Γ=A(A)E·E*, where A(λ) is thefunction of wavelength, and E* is the conjugate of scattering field Eand the total optical power due to scattering from SAS is an becalculated by the following equation

P = 2π∫₀^(π)Γ (θ)sin  θ 𝕕θ

This equation was utilized to calculate SAS values for Corning® SMF-28™optical fiber and for the optical waveguide fibers 10 described above.FIG. 4 shows a comparison of scattering curves (scattering data at thewavelength of 1550 nm) between Corning® SMF-28® and one embodiment ofthe optical waveguide fiber 10.

It can be seen that this new design has lower magnitude of scatteringand the range of scattering angle is smaller. Both lead to smaller totalscattering loss. Table 6 lists the calculated SAS, at differentwavelengths, for Corning® SMF-28® and ten embodiments of the opticalwaveguide fibers 10 corresponding to refractive index profiles on FIGS.2 a–2 c.

TABLE 6 SAS @ SAS @ SAS @ SAS @ 1300 nm 1400 nm 1550 nm 1600 nm Profile(dB/km) (dB/km) (dB/km) (dB/km) a 0.016 0.013 0.011 0.010 b1 0.004 0.0040.003 0.003 d 0.004 0.003 0.003 0.003 e 0.004 0.004 0.003 0.003 f 0.0040.003 0.003 0.003 g 0.004 0.004 0.003 0.003 h 0.010 0.009 0.007 0.007 I0.012 0.010 0.008 0.008 j 0.011 0.009 0.008 0.007 k 0.012 0.010 0.0080.008 SMF-28 ® 0.028 0.024 0.020 0.018

Table 7 lists the SAS values which are normalized by the SAS value ofthe SMF-28® fiber at the same wavelength, (where SAS of is SMF-28® isassumed to b 1)

TABLE 7 SAS @ SAS @ SAS @ SAS @ profile 1300 nm 1400 nm 1550 nm 1600 nma 0.55 0.55 0.56 0.57 b1 0.15 0.15 0.16 0.16 d 0.14 0.14 0.15 0.15 e0.15 0.15 0.16 0.16 f 0.14 0.14 0.14 0.14 g 0.15 0.16 0.16 0.16 h 0.360.37 0.37 0.38 I 0.41 0.42 0.43 0.43 j 0.39 0.39 0.40 0.40 k 0.42 0.430.43 0.44 SMF-28 ® 1 1 1 1

Table 8 lists the SAS values of each optical waveguide fiber (profiles(a)–(k)), when the SAS value of SMF-28® fiber is 0.1 dB/km at 1550 mm.All of these optical waveguide fiber (profiles (a)–(k)) have lower SAS,compared with that of SMF-28®, as shown in Tables 6–8. The highest SASvalue corresponds to profile (a), with SAS value of about 57% of that ofSMF-28®. The lowest SAS values correspond to profiles d, e and f, andare only about 20% or less (at 1550 nm) than that of SMF-28®.

TABLE 8 SAS @ SAS @ SAS @ SAS @ 1300 nm 1400 nm 1550 nm 1600 nm profile(dB/km) (dB/km) (dB/km) (dB/km) a 0.05 0.06 0.06 0.06 b1 0.02 0.02 0.020.02 d 0.01 0.01 0.01 0.01 e 0.02 0.02 0.02 0.02 f 0.01 0.01 0.01 0.01 g0.02 0.02 0.02 0.02 h 0.04 0.04 0.04 0.04 I 0.04 0.04 0.04 0.04 j 0.040.04 0.04 0.04 k 0.04 0.04 0.04 0.04 SMF-28 ® 0.15 0.12 0.10 0.09

In the wavelength range discussed herein (1300–1600 nm), SAS valuedecays with wavelength, proportionally to 1/λ^(p), where p is the powerindex of the wavelength. The SAS values of the SMF-28® fiber decay as

$\frac{1}{\lambda^{2.143}}.$The decay rate of optical waveguide fibers 10 corresponding to theprofiles (a)–(k) described herein is slower than that of the SMF-28®fiber, the values p are listed in Table 9, below.

TABLE 9 Fiber profile Power Index p a 1.996 b1 1.983 d 1.979 e 1.988 f1.983 g 1.988 h 1.962 I 1.967 j 1.967 k 1.974

The power indexes p (shown in Table 9) of the optical fiber 10 shavesmaller values than that of SMF-28® fiber (i.e., smaller than 2.143),which implies that small angle scattering decays slower than that ofSMF-28® fiber. This means the SAS of the optical fibers 10 changes moregradually than that of standard SMF-28® fiber, implying smaller SAS,which leads to lower overall fiber attenuation.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present inventionwithout departing from the spirit and scope of the invention. Thus it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. An optical waveguide fiber comprising comprising: a core with arefractive index profile having, a radius, an alpha and a relativerefractive index characterized by delta % that varies along said radius;at least one cladding surrounding said core; wherein said alpha is lessthan 2.5, peak refractive index delta % in said core is between 0.34%and 0.4%, said relative refractive index is less than 0.01% for allradii greater than 7 μm, and said optical waveguide fiber having a modefield diameter MFD at a wavelength of 1310 nm of no more than 9.54 μm,and attenuation less than: (a) 0.329 dB/km at a wavelength of 1310 nm,(b) 0.290 dB/km at a wavelength of 1383 nm, (c) 0.255 dB/km at awavelength of 1410 nm, and (d) 0.189 dB/km at a wavelength of 1550 nm.2. The optical waveguide fiber according to claim 1, wherein said MFD is9.2 μm to 9.4 μm, said optical waveguide fiber having zero dispersionwavelength between a 1309 nm and 1323 nm.
 3. The optical waveguide fiberaccording to claim 2, wherein said attenuation is not higher than: 0.322dB/km at a wavelength of 1310 nm, and 0.179 dB/km at a wavelength of1550 nm.
 4. The optical waveguide fiber according to claim 3, whereinsaid attenuation is not higher than: 0.270 dB/km at a wavelength of 1383nm, 0.247 dB/km at a wavelength of 1410 nm.
 5. The optical waveguidefiber according to claim 1, wherein said attenuation is not higher than:0.322 dB/km at a wavelength of 1310 nm, and 0.179 dB/km at a wavelengthof 1550 nm.
 6. The optical waveguide fiber according to claim 1, whereinsaid attenuation is not higher than: 0.270 dB/km at a wavelength of 1383nm, 0.247 dB/km at a wavelength of 1410 mm.
 7. The optical waveguidefiber according to claim 1, wherein said attenuation is less than: (a)0.322 dB/km at a wavelength of 1310 nm, (b) 0.270 dB/km at a wavelengthof 1383 nm; (c) 0.247 dB/km at a wavelength of 1410 nm, and (d) 0.179dB/km attenuation at a wavelength of 1550 nm.
 8. The optical waveguidefiber according to claim 1, wherein Small Angle Scattering (SAS) is lessthan 0.006 dB/km at the wavelength of 1550 nm.
 9. The optical waveguidefiber according to claim 8, wherein Small Angle Scattering (SAS) is lessthan 0.002 dB/km at the wavelength of 1550 nm.
 10. The optical waveguidefiber according to claim 1, wherein Small Angle Scattering (SAS) is lessthan 0.0081 dB/km at the wavelength of 1300 nm.
 11. The opticalwaveguide fiber according to claim 10, wherein Small Angle Scattering(SAS) is no more than 0.0025 dB/km at the wavelength of 1300 nm.
 12. Theoptical waveguide fiber according to claim 1, wherein Small AngleScattering (SAS) is less than 0.007 dB/km at the wavelength of 1400 nm.13. The optical waveguide fiber according to claim 12, wherein SmallAngle Scattering (SAS) is no more than 0.002 dB/km at the wavelength of1400 nm.
 14. The optical waveguide fiber according to claim 1, whereinsaid optical waveguide fiber has PinArray macrobend loss of less than 20dB at the wavelength of 1550 nm.
 15. The optical waveguide fiberaccording to claim 14, wherein said optical waveguide fiber has PinArraymacrobend loss of less than 10 dB at the wavelength of 1550 nm.
 16. Theoptical waveguide fiber according to claim 1, wherein said opticalwaveguide fiber has Lateral Load microbend loss of less than 1.2 dB/m atthe wavelength of 1550 nm.
 17. The optical waveguide fiber according toclaim 16, wherein said optical waveguide fiber has Lateral Loadmicrobend loss of less than 0.7 dB/m at the wavelength of 1550 nm. 18.The optical waveguide fiber according to claim 1, wherein said opticalwaveguide fiber has a Stimulated Brillouin Scattering Threshold (SBSt)of higher than 8.5 dBm.
 19. The optical waveguide fiber according toclaim 1, wherein said optical waveguide fiber has a Stimulated BrillouinScattering Threshold (SBSt) between 8.2 dBm and 9.68 dBm.
 20. Theoptical waveguide fiber according to claim 1, wherein said opticalwaveguide fiber has PMD of less than 0.1 ps/sqrt(km).